diff --git a/README.md b/README.md
index 9265b45..02651fd 100644
--- a/README.md
+++ b/README.md
@@ -1,66 +1,150 @@
-## Foundry
+## blockchain-tools
 
-**Foundry is a blazing fast, portable and modular toolkit for Ethereum application development written in Rust.**
+**`blockchain-tools` is a Solidity library for bitcoin-related functionality written in Solidity.**
 
-Foundry consists of:
+It implements encoding/decoding bitcoin addresses. 
+Implementation is slightly optimized for Solidity (e.g. it uses the fact that uint256 is 256 bits).
+Currently, it supports:
+1. Segwit v0 address BIP-0173
+2. Segwit v1 address (taproot) BIP-0350 
+3. Encoding/decoding returns specific error thus making debugging much easier
+4. Almost all tests from [Python reference implementation](https://github.com/sipa/bech32/tree/master/ref/python) are implemented
 
--   **Forge**: Ethereum testing framework (like Truffle, Hardhat and DappTools).
--   **Cast**: Swiss army knife for interacting with EVM smart contracts, sending transactions and getting chain data.
--   **Anvil**: Local Ethereum node, akin to Ganache, Hardhat Network.
--   **Chisel**: Fast, utilitarian, and verbose solidity REPL.
+Solidity code for tests was generated automatically using scripts from `python_ref` dir. This scripts use test data and functions from [Python reference implementation](https://github.com/sipa/bech32/tree/master/ref/python) for BIP-0350.
 
-## Documentation
-
-https://book.getfoundry.sh/
+It uses an excellent tool [Foundry](https://book.getfoundry.sh/).
 
 ## Usage
 
-### Build
-
+### Install the library
 ```shell
-$ forge build
+$ forge install --no-commit https://github.com/stroomnetwork/blockchain-tools
 ```
 
-### Test
+### Add remappings
+Add the following line to file `remappings.txt`. If the file does not exist, create it.
+```
+blockchain-tools/=lib/blockchain-tools/src
+```
 
-```shell
-$ forge test
+### Import encoding/decoding library
+```solidity
+import {Bech32m} from "blockchain-tools/Bech32m.sol";
 ```
 
-### Format
+### To decode Bitcoin address
+```solidity
+(uint8 witVer, bytes memory data, Bech32m.DecodeError err) = Bech32m.decodeSegwitAddress(bytes("tb"), bytes("tb1p5z8wl5tu7m0d79vzqqsl9gu0x4fkjug857fusx4fl4kfgwh5j25spa7245"));
+```
 
-```shell
-$ forge fmt
+### To encode Bitcoin address
+```solidity
+bytes memory btcAddr = Bech32m.encodeSegwitAddress(bytes("tb"), 1, hex"a08eefd17cf6dedf15820021f2a38f3553697107a793c81aa9fd6c943af492a9");
 ```
 
-### Gas Snapshots
+## Sample Contract
+It includes one sample contract which calculates bitcoin address given an ethereum address `BTCDepositAddressDeriver`. pk = pk1 * hash(pk1 || bytes(eth_address)) + pk2 * hash(pk2 || bytes(eth_address)). pk1 and pk2 are public keys corresponding to two Taproot addresses. 
+It deterministically generate individual bitcoin address for an eth address. It can be used to bridge Bitcoin and Ethereum.
 
+By default `anvil` uses deterministic address generation from seed. So each launch of anvil will give the same addresses and private keys. For usability they are copy-pasted in `env-anvil` file.
+
+Commands for deploying and interacting are slightly large, so they were put in `Makefile`. Most commands have form `make <action>-<object>`.
+
+### Get Help
+```shell 
+$ make
+```
+OR
 ```shell
-$ forge snapshot
+$ make help
 ```
 
-### Anvil
+Prints help message with a list of available commands and some descriptions.
 
-```shell
-$ anvil
+### Build
+```shell 
+$ make build
+```
+builds the library.
+
+### Clean
+```shell 
+$ make clean
 ```
+Cleans output cache. Sometimes when renaming files and/or changing submodules very strange errors appear. Most probably due to `forge` caching. This command deletes project related cache file. Basically it deletes `cache` and `out` directories. 
 
-### Deploy
+NOTE: it is different from `$ forge clean`. I don't know why `$ forge clean` still leaves some files and thus it is not "complete" clean. Thus `$ make clean` was created.
 
+### Start anvil
 ```shell
-$ forge script script/Counter.s.sol:CounterScript --rpc-url <your_rpc_url> --private-key <your_private_key>
+$ make start-anvil
+``` 
+starts `anvil` with the default settings.
+
+### Deploy sample contract `BTCDepositAddressDeriver`
+```shell 
+$ make deploy-on-anvil
+``` 
+deploys `BTCDepositAddressDeriver` on the local anvil blockchain. It writes the deployed contract address to `temp/BTCDepositAddressDeriver.31337.address`.
+
+### Set seed in deployed contract
+```shell 
+$ make set-sample-seed
+``` 
+Set seed for previously deployed `BTCDepositAddressDeriver`. Btc seed addresses are hardcoded so the operation is deterministic.
+TODO: explain what contract address it uses.
+
+### Calculate bitcoin address from a given ethereum address
+```shell 
+$ make get-sample-btc-address
 ```
+Generate bitcoin address from an eth address. Eth address is hard-coded so this operation is deterministic.
 
-### Cast
+### Run unit tests
+```shell 
+$ make test
+``` 
+Run unit-tests.
 
-```shell
-$ cast <subcommand>
+### Run integration tests
+```shell 
+$ make test-sample-flow
+```
+Run integration test. Deploy contract, set seed, generate btc address. Check that the address is correct.
+
+Note: this command requires already running `anvil`. 
+
+### Run all tests
+```shell 
+$ make test-all
 ```
+Run both unit and integration tests.
 
-### Help
+Note: this command requires already running `anvil`. 
+
+## Using `cast`
+Cast is a command line tool for interacting with smart contracts. It is a part of Foundry.
+
+Private keys and RPC URL for default `anvil` configuration are stored in `env-anvil`. `anvil` uses deterministic key generation and thus keys are the same for different launches.
+To import these values.
+```shell
+$ source env-anvil
+```
 
+To get value of `btcAddr1` field.
 ```shell
-$ forge --help
-$ anvil --help
-$ cast --help
+$ cast call $(cat temp/BTCDepositAddressDeriver.31337.address) "btcAddr1()" --rpc-url $ANVIL_RPC_URL
 ```
+It returns value of `btcAddr` field in hex. 
+
+To get the value of `btcAddr` as string:
+```shell
+$ cast --to-utf8 $(cast call $(cat temp/BTCDepositAddressDeriver.31337.address) "btcAddr1()" --rpc-url $ANVIL_RPC_URL)
+``` 
+
+TODO: cast set-seed
+
+TODO: cast get eth address
+
+TODO: gas usage
+
diff --git a/src/Bech32m.sol b/src/Bech32m.sol
index a94664b..7340d51 100644
--- a/src/Bech32m.sol
+++ b/src/Bech32m.sol
@@ -319,7 +319,7 @@ library Bech32m {
         bytes memory hrp,
         uint8 witVer,
         bytes memory witProg
-    ) internal pure returns (bytes memory) {
+    ) public pure returns (bytes memory) {
         BechEncoding spec = witVer == 0
             ? BechEncoding.BECH32
             : BechEncoding.BECH32M;